Search Results (5)

In an attempt to explore the RNA viromes of two German rivers, we searched the virus particle contents of one 50 L water sample each from the Teltow Canal and the Havel River for viruses assumed to infect invertebrates. More than 330 complete and partial virus genomes up to a length of 37 kb were identified, with noda-like and reo-like viruses being most abundant, followed by bunya-like and birna-like viruses. Viruses related to the Permutotetraviridae, Nidovirales, Flaviviridae, Rhabdoviridae and Chuviridae as well as the unclassified Jῑngmén virus and Negev virus groups were also present. The results indicate a broad extent of recombinant virus genomes, supporting the concept of the modularity of eukaryotic viruses. For example, novel combinations of genes encoding replicase and structural proteins with a jellyroll fold have been observed. Less than 35 viruses could be assigned to existing virus genera. These are (i) an avian deltacoronavirus which was represented by only one short contig, albeit with 98% similarity, (ii) a seadornavirus and a rotavirus, and (iii) some 30 nodaviruses. All remaining viruses are novel and too diverse for accommodation in existing genera. Many of the virus genomes exhibit ORFans encoding hypothetical proteins of up to 2000 amino acids without conserved protein domains. Full article

The viromes of freshwater bodies are underexplored. The Picornavirales order, with 371 acknowledged species, is one of the most expansive and diverse groups of eukaryotic RNA viruses. In this study, we add 513 picorna-like viruses to the assemblage of more than 2000 unassigned picorna-like viruses. Our set of the aquatic Picornavirales virome of the Teltow Canal in Berlin, Germany, consists of 239 complete and 274 partial genomes. This urban freshwater body is characterized by the predominance of marna-like viruses (30.8%) and dicistro-like viruses (19.1%), whereas picornaviruses, iflaviruses, solinvi-like viruses, polycipi-like viruses, and nora-like viruses are considerably less prevalent. Caliciviruses and secoviruses were absent in our sample. Although presenting characteristic domains of Picornavirales, more than 100 viruses (20.8%) could not be assigned to any of the 9 Picornavirales families. Thirty-three viruses of the Marnaviridae—mostly locarna-like viruses—exhibit a monocistronic genome layout. Besides a wealth of novel virus sequences, viruses with peculiar features are reported. Among these is a clade of untypeable marna-like viruses with dicistronic genomes, but with the capsid protein-encoding open reading frame located at the 5′ part of their RNA. A virus with a similar genome layout but clustering with dicistroviruses was also observed. We further detected monocistronic viruses with a polymerase gene related to aparaviruses. The detection of Aichi virus and five novel posa-like viruses indicates a slight burden in municipal wastewater. Full article

Sponges are unusual representatives of the animal kingdom; their viromes, as part of the associated community, began to be studied quite recently, and, accordingly, these studies are gaining momentum. The diversity of viruses in sponges is high, and they most likely play a significant role in the composition of the sponge holobiont, especially under stress conditions. The objects of our metagenomic study were RNA viruses of two common endemic species of Baikal sponges, Lubomirskia baikalensis and Baikalospongia bacillifera. As a result of viral RNA sequencing, we were able to identify fragments of viral genomes related to those from the RefSeq NCBI complete viral genome database. Most of the similar genomes belonged to viruses isolated from various invertebrates; some of the scaffolds were related to known plant viruses, and one of them was related to a vertebrate virus. The similarity of the putative proteins of viral scaffolds from the Baikal sponges with proteins of known viruses turned out to be low (20.7–67.3%), indicating the detection of novel viruses. The samples of diseased and visually healthy sponges were clustered separately, suggesting a shift in sponge virome composition during the course of the disease. In a comparative analysis, the viromes of the Baikal and marine sponges differed significantly, demonstrating the influence of the host species, habitat, and geographical location on virome composition in the sponge holobiont. Full article

Crayfish are a keystone species of freshwater ecosystems and a successful invasive species. However, their pathogens, including viruses, remain understudied. The aim of this study was to analyze the virome of the invasive signal crayfish (Pacifastacus leniusculus) and to elucidate the potential differences in viral composition and abundance along its invasion range in the Korana River, Croatia. By the high-throughput sequencing of ribosomal RNA, depleted total RNA isolated from the crayfish hepatopancreas, and subsequent sequence data analysis, we identified novel and divergent RNA viruses, including signal crayfish-associated reo-like, hepe-like, toti-like, and picorna-like viruses, phylogenetically related to viruses previously associated with crustacean hosts. The patterns of reads abundance and calculated nucleotide diversities of the detected viral sequences varied along the invasion range. This could indicate the possible influence of different factors and processes on signal crayfish virome composition: e.g., the differences in signal crayfish population density, the non-random dispersal of host individuals from the core to the invasion fronts, and the transfer of viruses from the native co-occurring and phylogenetically related crayfish species. The study reveals a high, previously undiscovered diversity of divergent RNA viruses associated with signal crayfish, and sets foundations for understanding the potential risk of virus transmissions as a result of this invader’s dispersal. Full article

Charophyte algae, not chlorophyte algae, are the ancestors of ‘higher plants’; hence, viruses infecting charophytes may be related to those that first infected higher plants. Streamwaters from British Columbia, Canada, yielded single-stranded RNA metagenomes of Charavirus canadensis (CV-Can), that are similar in genomic architecture, length (9593 nt), nucleotide identity (63.4%), and encoded amino-acid sequence identity (53.0%) to those of Charavirus australis (CV-Aus). The sequences of their RNA-dependent RNA-polymerases (RdRp) resemble those found in benyviruses, their helicases those of hepaciviruses and hepegiviruses, and their coat-proteins (CP) those of tobamoviruses; all from the alphavirus/flavivirus branch of the ‘global RNA virome’. The 5’-terminus of the CV-Can genome, but not that of CV-Aus, is complete and encodes a methyltransferase domain. Comparisons of CP sequences suggests that Canadian and Australian charaviruses diverged 29–46 million years ago (mya); whereas, the CPs of charaviruses and tobamoviruses last shared a common ancestor 212 mya, and the RdRps of charaviruses and benyviruses 396 mya. CV-Can is sporadically abundant in low-nutrient freshwater rivers in British Columbia, where Chara braunii, a close relative of C. australis, occurs, and which may be its natural host. Charaviruses, like their hosts, are ancient and widely distributed, and thus provide a window to the viromes of early eukaryotes and, even, Archaea. Full article